You’ve done a good job on these David. I’m never satisfied with my results but over the past year, as I am starting to paint more often, things are improving, so keep going.
I too had problems with Union blue and highlights. Then I read Mike Blank’s Colour Harmony and started using his mixes, Prussian blue mixed with black for the base colour, darken with black, and he has a couple of mixes for highlights - Grey or a light pink mixed with the base colour. I found his book very useful for the colour mixes he offers. Well worth acquiring a copy.
I also took Mike Butler’s (Mike the Kiwi) and Mike Blank’s advice to enjoy the experience of experimenting. Mike Butler’s book Modelling and Painting World War I Allied Figures is also a gem, and well worth the money even if one doesn’t paint First World War figures, especially the techniques he uses to achieve unbelievable realism.
Cheers
Chris.
PS. You’d never get those seeds into Australia. Very tough quarantine regulations with heavy fines for not declaring them.